Method and apparatus for estimating the service life of a battery

ABSTRACT

A computer program is provided. The computer program product includes a medium readable by a computer, the medium (1) having means for inputting a signal representative of a temperature range in which a temperature of an operating environment of a battery resides; and (2) means for estimating a service life of the battery based on the signal. Other means are also provided.

This application is a divisional of U.S. patent application Ser. No.09/415,652, filed Oct. 12, 1999 now U.S. Pat. No. 6,191,556, which isincorporated herein in its entirety by reference.

FIELD OF THE INVENTION

The present invention relates generally to battery technology, and moreparticularly to a method and apparatus for estimating the service lifeof a battery.

BACKGROUND OF THE INVENTION

For years single use and rechargeable nickel-cadmium (NiCd) batterieshave been employed to power portable radios, shavers, laptop computers,non-volatile memory components, etc. NiCd batteries exhibit goodcapacity (i.e., the length of useable time between charges), reusability(i.e., the ability to be recharged) and service life (i.e., the lengthof time a battery may be used before a minimum useful battery capacity,such as 60% of the battery's maximum or “initial” capacity, isunachievable by re-charging). However, due to environmental concernsover the disposal of heavy metals such as cadmium, alternative batterytechnologies have been developed.

Nickel metal hydride (NiMH) batteries offer a more environmentallyfriendly alternative to NiCd batteries. NiMH batteries have bettercapacity than NiCd batteries, but suffer from poor battery service lifein hot operating environments (e.g., above 36° C.). For example, foroperating environments having a temperature of about 28° C. or less, theservice life of a NiMH battery is about 36 months. However, foroperating environments having a temperature of about 36° C. or higher,the service life of a NiMH battery is only about 19.5 months.

Because batteries typically are rated based on the worst case operatingenvironment (e.g., about 40° C. for NIMH batteries) even though actualbattery operating environments rarely approach the worst case operatingenvironment, NiMH batteries often are changed prematurely. The highcosts associated with service calls, service disruption and batterydisposal that accompany battery replacement necessitate longer batteryservice life.

SUMMARY OF THE INVENTION

To address the need for longer battery service life, a method and anapparatus for estimating the service life of a battery are provided.Specifically, battery service life is estimated based on the actualtemperature of the operating environment of a battery rather than on aworst case operating environment temperature. Preferably battery servicelife is estimated periodically or is otherwise “integrated” duringbattery operation to account for any changes in the operatingenvironment temperature of the battery during its operation and toaccount for both the present and the past operating environmenttemperatures of the battery. By estimating the service life of a batterybased on its actual operating environment temperature, a worst caseservice life need not be assumed for the battery, and the battery neednot be replaced prematurely. Maximum service life is therefore extractedfrom every battery.

In a first aspect of the invention, an apparatus is provided forestimating the service life of a battery. The apparatus includes atemperature measurement circuit that measures a temperature of anoperating environment of the battery and outputs a signal representativeof the temperature of the operating environment. The apparatus furtherincludes a controller coupled to the temperature measurement circuitthat receives the temperature signal therefrom and estimates the servicelife of the battery based on the temperature signal. Preferably, thetemperature measurement circuit outputs a signal representative of atemperature range in which the measured operating environmenttemperature resides and the controller estimates the service life of thebattery based on the temperature range signal output by the temperaturemeasurement circuit.

In a second aspect of the invention, a method is provided for estimatingthe service life of a battery by measuring a temperature of an operatingenvironment of the battery and by estimating the service life of thebattery based on the measured operating environment temperature.Preferably, measuring the temperature of the operating environment ofthe battery includes outputting a signal representative of a temperaturerange in which the measured operating environment temperature resides.The service life of the battery is estimated based on the temperaturerange signal.

In a third aspect of the invention, a computer program product isprovided for estimating the service life of a battery as describedabove. The inventive computer program product is carried by a mediumreadable by a computer (e.g., a carrier wave signal, a floppy disc, ahard drive, a random access memory, etc.).

Other objects, features and advantages of the present invention willbecome more fully apparent from the following detailed description ofthe preferred embodiments, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most digit of areference number identifies the drawing in which the reference numberfirst appears.

FIG. 1 is a schematic diagram of a novel service life estimation circuitfor estimating the service life of a battery in accordance with thepresent invention; and

FIG. 2 is a flow chart of a service life estimation algorithm for usewith the service life estimation circuit of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic diagram of a novel circuit (e.g., service lifeestimation circuit 100) for estimating the service life of a battery inaccordance with the present invention. The service life estimationcircuit 100 comprises a temperature measurement circuit 102 formeasuring the temperature of an operating environment of a battery andfor outputting a signal representative of the measured temperature; anda controller 104 coupled to the temperature measurement circuit 102 forreceiving the temperature signal and for estimating the service life ofthe battery based thereon.

In the preferred embodiment of the present invention, the temperaturemeasurement circuit 102 measures an operating environment temperature ofa battery and outputs to the controller 104 a temperature range signalthat indicates in which of a plurality of temperature ranges themeasured operating environment temperature resides. Within thecontroller 104 a counter is associated with each of the plurality oftemperature ranges set by the temperature measurement circuit 102. Eachcounter counts the amount of time the battery is operated within thetemperature range associated with the respective counter. The battery'stotal operation time thereby can be obtained by adding together thecounts of each counter.

Moreover, to determine if the battery's service life has been exceeded,and thus whether the battery should be replaced, a pro-rated operationtime (rather than the actual operation time) of the battery is computed(e.g., by multiplying any battery operation time at elevatedtemperatures by a pro-rate factor which is greater than one) to accountfor elevated temperature operation of the battery. The pro-ratedoperation time of the battery is compared to a maximum service life ofthe battery (e.g., the service life of the battery if the battery isoperated in a low temperature environment such as 28° C. or less for aNiMH battery). If the pro-rated operation time exceeds the maximumservice life of the battery, an alarm is generated to indicate that thebattery should be replaced. Thus, although battery life varies dependingon the environmental temperature in which the battery operates, theinvention allows for an accurate estimate of battery life regardless ofthe operating environment temperature.

With reference to FIG. 1, the temperature measurement circuit 102comprises a thermistor 106 (e.g., a Mitsubishi Materials CorporationModel No. TH20-3V103F thermistor or any other suitable thermistor)coupled to an encoder circuit 108 via a first voltage divider circuit110, and a second voltage divider circuit 112 coupled to the encodercircuit 108. The first voltage divider circuit 110 comprises a firstresistor 114 coupled between a power supply rail (V_(cc)) and athermistor node 116, and a second resistor 118 coupled between thethermistor node 116 and ground. The thermistor 106 also is coupledbetween the thermistor node 116 and ground.

The second voltage divider circuit 112 comprises a third resistor 120coupled between the power supply rail (V_(cc)) and a first referencenode 122, a fourth resistor 124 coupled between the first reference node122 and a second reference node 126, a fifth resistor 128 coupledbetween the second reference node 126 and a third reference node 130,and a sixth resistor 132 coupled between the third reference node 130and ground. As described further below, each voltage divider circuit110, 112 generates one or more reference voltages based on a commonvoltage supply (e.g., the power supply rail (V_(cc)). Accordingly, thepower supply rail (V_(cc)) need not be tightly regulated because anyvoltage fluctuations present thereon will have an equivalent affect oneach voltage divider circuit (and any reference voltage or voltagesgenerated thereby). It will be understood that regulated referencevoltages and conventional regulation circuitry associated therewith(e.g., Zener diodes and the like) may be employed to generated thevarious reference voltages described herein.

The encoder circuit 108 comprises a first comparator 134, a secondcomparator 136 and a third comparator 138 each having a positive inputterminal coupled to the thermistor node 116. The negative inputterminals of the first comparator 134, the second comparator 136 and thethird comparator 138 are coupled to the first reference node 122, to thesecond reference node 126 and to the third reference node 130,respectively. The output of the second comparator 136 serves as an “X”output of the encoder circuit 108 and the outputs of the firstcomparator 134 and the third comparator 138 are combined via an XOR gate140 to serve as a “Y” output of the encoder circuit 108. The comparators134-138 may comprise any conventional comparator, but preferablycomprise comparators having hysteresis (such as Maxim Corporation ModelNo. MAX8214 comparators) so as to limit toggling of the X and Y outputsof the encoder circuit 108 as described below. Note that a decouplingcapacitor 141 preferably is coupled between the power supply rail(V_(cc)) and ground for noise reduction purposes as is known in the art.

In operation, the temperature measurement circuit 102 generates a twobit output signal (e.g., outputs X, Y of the encoder circuit 108) thatindicates in which of four temperature ranges the temperature (asmeasured by the thermistor 106) of an operating environment of a batteryresides. Specifically, as shown in TABLE 1 below, the thermistor 106 hasa resistance (R₁₀₆) that varies with temperature from about 10 Kohms at25° C. to about 6.258 Kohms at 36° C. In response to the resistancevariations of the

TABLE 1 T R₁₀₆ V₁₁₆ V₁₂₂ V₁₂₆ V₁₃₀ (° C.) (ohms) (volts) (volts) (volts)(volts) Y X 25 10K 2.075 2.007 1.910 1.808 0 1 28  8.77K 2.005 2.0071.910 1.808 1 1 32  7.392K 1.907 2.007 1.910 1.808 1 0 36  6.258K 1.8052.007 1.910 1.808 0 0

thermistor 106, the first voltage divider circuit 110 generates atemperature-sensitive voltage signal at the node 116 (V₁₁₆) that dependson the resistance (R₁₀₆) of the thermistor 106, the resistance (R₁₁₄) ofthe first resistor 114, the resistance (R₁₁₈) of the second resistor 118and the power supply rail voltage (V_(cc)) via equation (1) below:$\begin{matrix}{V_{116} = {{V_{cc}\frac{R_{TOTAL}}{R_{TOTAL} + R_{114}}\quad {where}\quad R_{TOTAL}} = \frac{R_{106}R_{118}}{R_{106} + R_{118}}}} & (1)\end{matrix}$

TABLE 1 lists values for the temperature-sensitive voltage signal (V116)at operating environment temperatures of 25° C., 28° C., 32° C. and 36°C. (for the resistance values listed in TABLE 2).

TABLE 2 R₁₁₄ R₁₁₈ R₁₂₀ R₁₂₄ R₁₂₈ R₁₃₂ (ohms) (ohms) (ohms) (ohms) (ohms)(ohms) 6.04K 7.50K 60.4K 1.96K 2.05K 36.5K

The temperature-sensitive voltage signal (V₁₁₆) is fed to the negativeinput terminal of each of the comparators 134-138, while the positivevoltage terminal of each comparator 134-138 is held at a referencevoltage V₁₂₂, V₁₂₆ and V₁₃₀, respectively (the voltages of the first,second and third reference nodes 122, 126, 130). The reference voltagesV₁₂₂, V₁₂₆ and V₁₃₀ are set by the second voltage divider circuit 112and are governed by equations (2)-(4) below: $\begin{matrix}{V_{122} = {V_{CC}\frac{R_{124} + R_{128} + R_{132}}{R_{120} + R_{124} + R_{128} + R_{132}}}} & (2) \\{V_{126} = {V_{CC}\frac{R_{128} + R_{132}}{R_{120} + R_{124} + R_{128} + R_{132}}}} & (3) \\{V_{130} = {V_{CC}\frac{R_{132}}{R_{120} + R_{124} + R_{128} + R_{132}}}} & (4)\end{matrix}$

where R₁₂₀, R₁₂₄, R₁₂₈ and R₁₃₂ are the resistances, respectively, ofthe resistors 120-132. TABLE 1 lists the values of the first, second andthird reference voltages V₁₂₂, V₁₂₆, V₁₃₀ of the first, second and thirdreference nodes 122, 126, 130, respectively, for the resistance valueslisted in TABLE 2.

With the reference voltage of each comparator 134-138 thus fixed, eachcomparator 134-138 outputs a positive voltage level (e.g., V_(cc)) ifthe temperature-sensitive voltage signal (V₁₁₆) is greater than thecomparator's reference voltage, and outputs zero volts if thetemperature-sensitive voltage signal (V₁₁₆) is less than thecomparator's reference voltage. For example, with reference to TABLE 1,if the operating environment temperature of a battery (as measured bythe thermistor 106) is 25° C. or less, the temperature-sensitive voltagesignal (V₁₁₆) exceeds the first, the second and the third referencevoltages V₁₂₂, V₁₂₆ and V₁₃₀. Each comparator output is driven high(e.g., to V_(cc)), and in response thereto, the X output of the encodercircuit 108 is driven high by the second comparator 136 and the Y outputof the encoder circuit 108 is driven low by the XOR gate 140.

The temperature-sensitive voltage signal (V₁₁₆) remains above all threereference voltages V₁₂₂, V₁₂₆ and V₁₃₀ until a temperature of about 28°C. when the temperature-sensitive voltage signal (V₁₁₆) no longerexceeds the first reference voltage V₁₂₂, but remains in excess of thesecond and third reference voltages V₁₂₆, V₁₃₀. With the first referencevoltage V₁₂₂ no longer exceeded, the output of the first comparator 134is low while the outputs of the second and third comparators 136, 138remain high. In response thereto, the X output of the encoder circuit108 remains high (due to the high voltage level output by the secondcomparator 136) while the Y output of the encoder circuit 108 is drivenhigh (e.g., due to the low voltage level and the high voltage level fromthe first and third comparators 134, 138, respectively, fed to the XORgate 140).

Note that because the comparators 134-138 preferably have hysteresisassociated therewith, once the temperature-sensitive voltage signal(V₁₁₆) exceeds a reference voltage associated with one of thecomparators 134-138, and the comparator's output voltage switchespolarity in response thereto, the comparator's output polarity willremain in its new polarity state despite small variations in the voltagesignal (V₁₁₆) about the reference voltage. In this manner, smalltemperature fluctuations about a temperature that represents atemperature range “boundary” of the temperature measurement circuit 102(e.g., about 28° C., 32° C. or 36° C.) will not cause the X and Youtputs of the encoder circuit 108 to transition. The number of X and Youtput transitions thereby is reduced, as is the likelihood that thecontroller 104 will read a transitorial and potentially false voltagelevel on either the X or Y output during battery service life estimation(described below). To further reduce potential false voltage levelreadings by the controller 104, the X and Y outputs of the encodercircuit 108 switch polarity using a “grey code” scheme wherein only oneof the X and Y outputs switches polarity when a temperature rangeboundary is reached. Accordingly, even if the controller 104 erroneouslyreads one of the X and Y outputs before or while it transitions, andidentifies an improper temperature range based thereon, the improperlyidentified temperature range will be within one temperature range of theproper temperature range (e.g., minimizing the error). A grey codescheme also eliminates any potential false readings by the controller104 due to differing switching rates of the X and Y outputs of theencoder circuit 108.

The temperature-sensitive voltage signal (V₁₁₆) remains above the secondand third reference voltages V₁₂₆, V₁₃₀ until a temperature of about 32°C. when the temperature-sensitive voltage signal (V₁₁₆) no longerexceeds the second reference voltage V₁₂₆, but remains in excess of thethird reference voltage V₁₃₀. With the first and second referencevoltages V₁₂₂, V₁₂₆ no longer exceeded, the outputs of the first andsecond comparators 134, 136 are low while the output of the thirdcomparator 138 remains high. In response thereto, the X output of theencoder circuit 108 is driven to zero volts by the second comparator 136while the Y output of the encoder circuit 108 remains high (as thevoltage levels that feed the XOR gate 140 remain unchanged).

The temperature-sensitive voltage signal (V₁₁₆) remains above the thirdreference voltage V₁₃₀ until a temperature of about 36° C. is reached.Thereafter, with no reference voltage exceeded, the output of eachcomparator 134-138 is driven low, as are the X and Y outputs of theencoder circuit 108. Because the temperature-sensitive voltage (V₁₁₆)continues to decrease with increasing temperature, the X and Y outputsremain low for all temperatures in excess of 36° C.

In summary, the temperature measurement circuit 102 measures atemperature of an operating environment of a battery (via the thermistor106) and outputs a signal (the X and Y outputs) that represents atemperature range in which the measured operating temperature resides.In the preferred embodiment of FIG. 1, an embodiment specificallyadapted for use with NiMH batteries, the four temperature ranges inwhich a measured temperature may reside (and the corresponding X and Youtputs from the encoder circuit 108) are listed in TABLE 3. It will beunderstood that the temperature measurement circuit 102 may beconfigured for use with other batteries and/or other or more temperatureranges if desired.

TABLE 3 TEMPERATURE RANGE (° C.) Y OUTPUT X OUTPUT <28 0 1 about 28-32 11 about 32-36 1 0 >36 0 0

The controller 104 receives the X and Y outputs (e.g., the temperaturerange signal) from the temperature measurement circuit 102 and estimatesthe service life of a battery based thereon (as described below).Preferably the controller 104 comprises a microcontroller ormicroprocessor such as an IBM PowerPC™ 403 processor having program codestored therein that performs battery service life estimation functions.For example, the X and Y outputs of the temperature measurement circuit102 may be input by an input/output (I/O) module 142 of the controller104 (e.g., via I/O pins (not shown) of an I/O port 144 of the controller104). The temperature range information encoded by the X and Y outputs(TABLE 3) then may be used by software (e.g., program code) within arandom access or read only memory (represented generally by referencenumber 146) of the controller 104 for battery service life estimation asdescribed below. Alternatively, hardware (e.g., discreet counters, logicmodules, application specific integrated circuits, etc.) or acombination of hardware and software may be similarly employed.

The operation of the controller 104 is now described with reference toFIG. 1 and with reference to FIG. 2 which is a flow chart of a preferredservice life estimation algorithm 200. It is assumed that a new batterysuch as a NiMH battery (not shown) having its maximum service liferemaining (e.g., 36 months for an operating temperature of about 28° C.or less) is monitored by placing the thermistor 106 proximate thebattery (e.g., on, next to or sufficiently close to the battery tomonitor the operating environment temperature of the battery).

With reference to FIG. 2, in step 201, the service life estimationalgorithm 200 begins. In step 202, a counter is initialized (e.g., iscreated and is set to zero) for each temperature range to be monitored.For the preferred embodiment of the service life estimation circuit 100of FIG. 1, four temperature ranges may be monitored as shown in TABLE 3(e.g., less than about 28° C., between about 28-32° C., between about32-36° C. and greater than about 36° C.). Accordingly, four counters148, 150, 152 and 154 are initialized for (i.e., are associated with)the temperature ranges of less than about 28° C., between about 28-32°C., between about 32-36° C. and greater than about 36° C., respectively.The counters 148-154 preferably are software-based, 8-byte countersdefined within the memory 146 as is known in the art. It will beunderstood that the spatial boundaries and arrangement of the counters148-154 in FIG. 1 are arbitrary and are shown merely for convenience.

Following initialization of the counters 148-154, in step 203 thecontroller 104 waits or “sleeps” for a predetermined time period (e.g.,to allow the battery to age). The preferred sleep period for thecontroller 104 is about 5 minutes although any other time period (ifany) may be employed.

In step 204, the temperature range signal (e.g., the X and Y outputs) ofthe temperature measurement circuit 102 is sampled to identify in whichof the four temperature ranges the current operating environmenttemperature of the battery resides (e.g., below about 28° C., betweenabout 28-32° C., between about 32-36° C. or above about 36° C.).Specifically, program code within the memory 146 (represented in FIG. 1as estimation and processing code 156 for convenience) directs the I/Omodule 142 to input the voltage levels of the X and Y inputs.Thereafter, in step 205, the estimation and processing code 156interprets these voltage levels in accordance with TABLE 3 to determinein which temperature range the current operating environment temperatureof the battery resides. The counter associated with the temperaturerange also is identified.

In step 206, the estimation and processing code 156 adds the sleep timeof the controller 104 (e.g., the time between temperature samples) tothe count of the counter associated with the temperature rangeidentified by the X and Y outputs of the temperature measurement circuit102. For example, if in step 205 the estimation and processing code 156determines that the operating environment temperature of the batteryresides within the temperature range from about 28° C. to 32° C. (e.g.,because the X and Y outputs of the temperature measurement circuit 102have high logic levels), the estimation and processing code 156increases the count of the second counter 150 by the sleep time of thecontroller 104 (e.g., by about 5 minutes).

In step 207, the estimation and processing code 156 computes the totaloperation time of the battery by adding together the count of eachcounter 148-154. To compensate for the decrease in battery service lifefrom its maximum value (e.g., 36 months for NiMH batteries operated atabout 28° C. or less) that accompanies battery operation at elevatedtemperatures, a pro-rate factor is assigned to each counter 148-154 thatweights the count of each counter 148-154 based on the temperature rangeassociated with the counter. Specifically, the counts of counters havinghigh temperature ranges associated therewith (e.g., counters 152 and154) are weighted more heavily than the counts of counters having lowtemperature ranges associated therewith (e.g., counters 148 and 150) sothat when the battery is operated at temperatures above about 28° C. thecomputed operating time of the battery exceeds the actual operating timeof the battery. The battery thereby is aged more quickly when operatedat higher temperatures. Preferably, the pro-rate factor for the count ofthe first counter 148 (C₁₄₈) is 1.0, the pro-rate factor for the countof the second counter 150 (C₁₅₀) is 1.22, the pro-rate factor for thecount of the third counter 152 (C₁₅₂) is 1.50 and the pro-rate factorfor the count of the fourth counter 154 (C₁₅₄) is 1.83. The pro-ratedoperation time (T_(PRORATED)) of the battery therefore is governed byequation (5) below:

T _(PRORATED) =C ₁₄₈+1.22C ₁₅₀+1.5C ₁₅₂+1.83C ₁₅₄  (5)

In this manner, if a battery is operated at a temperature of about 28°C. or less, the battery is aged at its actual rate (so that an effectiveservice life of 35.75 months is employed for the battery), but if thebattery is operated at a temperature of about 36° C. or higher, thebattery is aged at 1.83 times its actual rate (so that an effectiveservice life of 19.5 months is employed for the battery). The battery isaged at an intermediate rate for intermediate temperature operation.Further, by including the time the battery is operated within eachtemperature range during battery service life estimation, both thepresent and the past operating environment temperatures of the batteryare considered during battery life estimation. Accordingly, an accurateestimation of battery service life is computed even if a battery isoperated at several different operating environment temperatures duringits lifetime. Note that for a binary count, pro-rate factors of 1.25,1.5 and 1.875 may be obtained by appropriate shifting and additionoperations as will be apparent to one of ordinary skill in the art(e.g., to generate 1.875X for a count of X, the count X may be added tothe count X shifted to the right by 1 bit, shifted to the right by 2bits and shifted to the right by 3 bits).

In step 208, the estimation and processing code 156 compares thepro-rated operation time of the battery to the maximum service life ofthe battery (e.g., the service life of the battery if operated at 28° C.or less). If the pro-rated operation time of the battery is less thanthe maximum service life of the battery, control passes to step 203, andsteps 203-207 are repeated (e.g., the controller 104 sleeps, a newtemperature range signal is sampled, the controller sleep time is addedto the appropriate counter and the pro-rated operation time iscomputed). This process is repeated until the pro-rated operation timeexceeds the maximum service life of the battery, after which timecontrol passes to step 209.

In step 209, the estimation and processing code 156 generates a signal(e.g., an alarm signal output by the I/O module 142 of the controller104) to indicate that the service life of the battery has been exceededand that the battery should be replaced. In step 210, the service lifeestimation algorithm 200 ends.

The foregoing description discloses only the preferred embodiments ofthe invention, modifications of the above disclosed apparatus and methodwhich fall within the scope of the invention will be readily apparent tothose of ordinary skill in the art. For instance, while the presentinvention has been described primarily with reference to NiMH batteries,other battery technologies may similarly benefit from the invention.Other temperature measurement means than the thermistor 106 such as asilicon pn-junction diode may be employed, as may other resistancevalues for the resistors 114-132, other temperature ranges and otherpro-rate factors.

Accordingly, while the present invention has been disclosed inconnection with the preferred embodiments thereof, it should beunderstood that other embodiments may fall within the spirit and scopeof the invention, as defined by the following claims.

The invention claimed is:
 1. A computer program product comprising: amedium readable by a computer, the computer readable medium having:means for inputting a signal representative of a temperature range inwhich a temperature of an operating environment of a battery resides;and means for estimating a service life of the battery based on thesignal.
 2. The computer program product of claim 1 wherein the means forestimating the service life of the battery comprises: means fordetermining a time the battery is operated within each of a plurality oftemperature ranges; and means for estimating the service life of thebattery based on the time the battery is operated within each of theplurality of temperature ranges.
 3. The computer program product ofclaim 1 wherein the means for estimating the service life of the batterycomprises means for estimating the service life of the battery based onthe time the battery is operated within each of the plurality oftemperature ranges and based on a pro-rate factor for each temperaturerange.
 4. The computer program product of claim 1 wherein the means forestimating the service live of the battery comprises: a plurality ofcounter means, each counter means having a count and a temperature rangeassociated therewith, each counter means for counting a time the batteryis operated within the temperature range associated with the countermeans; and estimation means for estimating the service life of thebattery based on the count of each counter means.
 5. The computerprogram product of claim 4 wherein the estimation means comprises meansfor estimating the service life of the battery based on the count ofeach counter means and a pro-rate factor for each counter means thatdepends on the temperature range associated with the counter means. 6.The computer program product of claim 5 wherein the plurality of countermeans comprise: a first counter means having a temperature range of lessthan about 28° C. associated therewith; a second counter means having atemperature range of between about 28° C. and about 32° C. associatedtherewith; a third counter means having a temperature range of betweenabout 32° C. and about 36° C. associated therewith; and a fourth countermeans having a temperature range of greater than about 36° C. associatedtherewith.
 7. The computer program product of claim 6 wherein: thepro-rate factor for the first counter means is about 1.0; the pro-ratefactor for the second counter means is about 1.22; the pro-rate factorfor the third counter means is about 1.5; and the pro-rate factor forthe fourth counter means is about 1.83.
 8. The computer program productof claim 1 further comprising means for periodically estimating theservice life of the battery.
 9. The computer program product of claim 8further comprising means for estimating the service life of the batteryabout every 5 minutes.
 10. The computer program product of claim 1further comprising means for generating an alarm if a maximum servicelife of the battery is exceeded.
 11. The computer program product ofclaim 1 wherein the means for inputting a signal comprises means forinputting at least one bit representative of the temperature range inwhich the operating environment temperature of the battery resides. 12.The computer program product of claim 11 wherein the means for inputtinga signal comprises means for inputting a plurality of bits indicative ofthe temperature range in which the operating environment temperatureresides.